The present invention is directed to cell and battery enclosures. A design and process are introduced for making a hermetically sealed thermocompression feedthrough and a peripheral seal for high temperature lithium-based battery applications.
It is necessary to provide an electrical feedthrough in electrochemical cell and battery enclosures, and it has been known to use ceramic-to-metal/ceramic techniques which are largely based on brazing principles and ceramic surface metallization, or compact powder techniques which are economical in fabrication costs which do not provide adequate hermeticity for high-temperature lithium-based battery applications. Accordingly, it is a goal of the present invention to provide an improved seal for the electrical feedthrough for a lithium-based electrochemical cell and battery enclosures.
U.S. Pat. No. 4,037,027 to Desplanches et al describes the use of thermocompression for making a seal between a metallic container and an .alpha.-Alumina ring for a sodium-sulphur high temperature cell. However, the technique and materials disclosed are not effective for lithium-based cells.
A peripheral seal provides a container for the cell electrochemistry and makes bipolar stacks of cells viable. The seal has to be a good electrical insulator at the cell high operating temperature (400.degree.-500.degree. C.), chemically stable at this high temperature, must match the thermal expansion of the cell components, have strong mechanical bonding to metals and/or ceramics, and provide a barrier to molten salt. Accordingly, it is a goal of the present invention to provide an improved peripheral seal for a lithium-based electrochemical battery applications.